Morale

Morale is needed to keep duplicants happy. The exact morale needed to do so is based on the duplicant's job. Poor morale will rapidly increase their Stress until they break, so it is recommended that upper level jobs are saved until several morale improvements are made.

As of "Meep's Mandatory Recreation Content Pack" Upgrade, if duplicants have a morale higher than expected, they can become Overjoyed, giving them short lasting but strong buffs, such as higher skills, improvements to buildings' decor, etc...so if one wishes to have overjoyed duplicants, it is recommended to make a lot of furniture buildings as well as Recreation rooms to keep duplicants overjoyed more often.

Morale table
Моральный дух